1. Field of the Invention
The invention relates to a method and a system for ensuring maximum reaction times in a data processing system, particularly between a safe input signal and the corresponding safe output signal.
2. Description of Related Art
In communicating data processing systems or installations, data in a message are usually valid only at a particular time or for a particular time because, particularly in the case of safety-related input/output signals, stipulated reaction times need to be observed.
On the basis of the prior art, delay time monitoring between transmitter and receiver is usually performed for this purpose. For receiver-end delay time monitoring, the transmitter appends an appropriate time information item to the data, with both the transmitter and the receiver needing to track the time. For transmitter-end monitoring, reception of the data is acknowledged to the transmitter by returning an acknowledgement signal, this additionally allowing the correct data sequence to be monitored.
Assuming that the data transmission comprises signals transmitted continuously and in the correct time sequence, German patent specification DE-101 02 435-C2 also discloses a method which ensures that a safe data transmission is checked, on the one hand, and also ensures a maximum possible or feasible delay in the transmission of a subsequent signal. This involves the specific proposal that data processing units which communicate with one another transmit data by initiating the sending of a subsequent signal only in response to a minimum time elapsing between two successive signals and in response to an acknowledgement signal from the receiving unit being received at the transmitter end.